The invention relates to an automatic gear ratio reduction system. In particular, the invention relates to a system that automatically adjusts a gear ratio between a drive source and a driven load sufficiently to maintain rotation of the driven load, in accordance with the resistance to rotation presented by the load.
A rotary power source, such as a motor, is generally not coupled directly with a load. Typically the motor has an operating rotational speed and torque. It is rare that this rotational speed is directly matched with the requirements of the load. For a given power, rotational speed and torque are inversely proportional. Thus, Accordingly, various transmission systems are employed to either reduce or increase the ratio between speed and torque to achieve a compromise, which best suits the load.
Many applications, however, will vary the torque/rotational speed requirements under different operating conditions. For example, an automobile initially begins motion with low rotational speed of the tires, but supplies high torque to the tires that allows the automobile to accelerate to a higher speed of travel. When the automobile reaches its cruising speed, the tires must be rotated at a higher speed, while less torque is necessary to accelerate the automobile. Accordingly, automobile transmissions have several gear ratios. The lowest gears are suitable for lower travel speeds and for a greater ability to accelerate, while the highest gears are suitable for cruising at higher speeds while keeping the engine within its designed range of rotational speed. Naturally, less torque and thereby less ability to accelerate is available when using the highest gears. Generally, automobiles have three to six fixed gear ratios between the engine and the xe2x80x98final drivexe2x80x99. Picking one of the gear ratios requires xe2x80x98shifting gearsxe2x80x99, either manually, or through an automatic mechanism.
In addition, common power tools undergo a similar battle for torque and rotational speed. A drill, for example, will commonly rotate at a high speed while it travels with little resistance through a workpiece. At times, however, the drill bit will encounter considerable resistance, which has a tendency to stall the drill. A stalled electric drill motor will draw considerable current, may overheat, and will shorten the useful life of the motor. Ordinarily, a drill stall causes the worker to halt working to prevent damaging the drill.
Various transmissions have been proposed which seek to allow the gear ratio to be altered continuously. So-called xe2x80x98continuously variable transmissionsxe2x80x99 supposedly allow infinite gear ratios to be achieved within a range. Such systems however, generally rely on belts, selective friction, and slippage, which thereby greatly decrease their efficiency and useful life.
While these units may be suitable for the particular purpose employed, or for general use, they would not be as suitable for the purposes of the present invention as disclosed hereafter.
It is an object of the invention to provide a gear ratio adjustment system that automatically adjusts the gearing ratio to achieve the necessary torque to maintain rotational motion at the load. Accordingly, the system reacts in response to increased resistance at the load to lower the gear ratio, increase the torque at the load, and thereby maintain motion.
It is another object of the invention to provide a gear ratio adjustment system which substantially operates using gears in mesh, and does not require xe2x80x98shifting of gearsxe2x80x99 or otherwise altering the arrangement of gears in mesh to achieve different gear ratios. Accordingly, the system effectively lowers the gear ratio while all gears remain in mesh.
It is a further object of the invention to provide a gear ratio adjustment system, which quickly adapts to changes in resistance upon the output gear, without stopping motion. Accordingly, the configuration of gears according to the present invention according to a primary embodiment employs an input/output gear set that allows the gear ratio to be lowered by the automatic commencement of planetary motion of the lower variance determining gear around the lower motion transfer gear mounted radially off center on a variance gear coaxial with the input and output gears, to compensate for the increased resistance at the output gear, wherein the lower variance gear is in part rotating the output gear through the lower motion transfer gear and in part orbiting around the lower motion transfer gear.
It is yet a further object of the invention to provide a gear ratio adjustment system, which allows continuous gear ratios to be achieved. Accordingly, the amount of resistance presented to the output gear will vary the degree to which the lower variance determining gear directly turns the lower motion transfer gear and the degree to which the lower variance determining gear revolves around the lower motion transfer gear. The partial direct rotation of the lower variance determining gear and revolution around the lower motion transfer gear by the lower variance determining gear will depend on the amount of resistance and will thereby achieve a xe2x80x98comfortablexe2x80x99 gear ratio by which rotation may continue.
It is a still further object of the invention to help ensure that the lower gear ratio associated with planetary motion only occurs when the resistance to rotation renders it necessary to lower the gear ratio. Accordingly, pressure can be applied to the variance gear of the input/output gear set to help ensure to increase the resistance necessary to begin lowering the effective gear ratio between the input and output gear set.
It is yet another object of the invention to provide a feedback loop which automatically increases the range of gear ratios achievable by the system. Accordingly, a variance control gear set is provided which is a substantial clone of the input/output gear set, except wherein the input gear is known as a speed gear which is driven by the output gear of the input/output gear set; and the output gear is a control gear which drives the variance gear of the input/output gear set.
To the accomplishment of the above and related objects the invention may be embodied in the form illustrated in the accompanying drawings. Attention is called to the fact, however, that the drawings are illustrative only. Variations are contemplated as being part of the invention, limited only by the scope of the claims.